Surface acoustic wave modulation of single photon emission from GaN/InGaN nanowire quantum dots

On-chip quantum information processing requires controllable quantum light sources that can be operated on-demand at high-speeds and with the possibility of in-situ control of the photon emission wavelength and its optical polarization properties. Here, we report on the dynamic control of the optical emission from core-shell GaN/InGaN nanowire (NW) heterostructures using radio frequency surface acoustic waves (SAWs). The SAWs are excited on the surface of a piezoelectric lithium niobate crystal equipped with a SAW delay line onto which the NWs were mechanically transferred. Luminescent quantum dot (QD)-like exciton localization centers induced by compositional fluctuations within the InGaN nanoshell were identified using stroboscopic micro-photoluminescence (micro-PL) spectroscopy. They exhibit narrow and almost fully linearly polarized emission lines in the micro-PL spectra and a pronounced anti-bunching signature of single photon emission in the photon correlation experiments. When the nanowire is perturbed by the propagating SAW, the embedded QD is periodically strained and its excitonic transitions are modulated by the acousto-mechanical coupling, giving rise to a spectral fine-tuning within a ~1.5 meV bandwidth at the acoustic frequency of ~330 MHz. This outcome can be further combined with spectral detection filtering for temporal control of the emitted photons. The effect of the SAW piezoelectric field on the QD charge population and on the optical polarization degree is also observed. The advantage of the acousto-optoelectric over other control schemes is that it allows in-situ manipulation of the optical emission properties over a wide frequency range (up to GHz frequencies).Comment: arXiv admin note: text overlap with arXiv:1902.0791

Carrier and Light Trapping in Graded Quantum Well Laser Structures

We investigated the carrier and light trapping in GaInAs/AlGaAs single quantum well laser structures by means of time resolved photoluminescence and Raman spectroscopy. The influence of the shape and depth of the confinement potential and of the cavity geometry was studied by using different AlGaAs/GaAs short-period superlattices as barriers. Our results show that grading the optical cavity improves considerably both carrier and light trapping in the quantum well, and that the trapping efficiency is enhanced by increasing the graded confining potential.Comment: PDF-format, 15 pages (including 4 figures), Applied Physics Letters (June 2000

Organisation of Prostate Cancer Services in the English National Health Service.

AIMS: The National Prostate Cancer Audit (NPCA) started in April 2013 with the aim of assessing the process of care and its outcomes in men diagnosed with prostate cancer in England and Wales. One of the key aims of the audit was to assess the configuration and availability of specialist prostate cancer services in England. MATERIALS AND METHODS: In 2014, the NPCA undertook an organisational survey of all 143 acute National Health Service (NHS) Trusts and 48 specialist multidisciplinary team (MDT) hubs cross England. Questionnaires established the availability and location of core diagnostic, treatment and patient-centred support services for the management of non-metastatic prostate cancer in addition to specific diagnostic and treatment procedures that reflect the continuing evolution of prostate cancer management, such as high-intensity focused ultrasound (HIFU) and stereotactic body radiotherapy. RESULTS: The survey received a 100% response rate. The results showed considerable geographical variation with respect to the availability of core treatment modalities, the size of the target population and catchment areas served by specialist MDT hubs, as well as in the uptake of additional procedures and services. Specifically there are gaps in the availability of core radiotherapy procedures; high dose rate and low dose rate brachytherapy are available in 44% and 75% of specialist MDTs, respectively. By comparison, there seems to be a relative 'over-penetration' of surgical innovation, with 67% of specialist MDTs providing robotic-assisted laparoscopic prostatectomy and 21% HIFU. There is also evidence of increased centralisation of core surgical procedures and regional inequity in the availability of surgical innovation across England. CONCLUSIONS: The organisational survey of the NPCA has provided a comprehensive assessment of the structure and function of specialist MDTs in England and the availability of prostate cancer procedures and services. As part of the prospective audit, the NPCA will assess the effect of the availability of prostate cancer services on access regionally and subsequent outcomes of care according to evidence-based guidelines

Centralisation of services for children with cleft lip or palate in England: a study of hospital episode statistics.

BACKGROUND: In 1998, a process of centralisation was initiated for services for children born with a cleft lip or palate in the UK. We studied the timing of this process in England according to its impact on the number of hospitals and surgeons involved in primary surgical repairs. METHODS: All live born patients with a cleft lip and/or palate born between April 1997 and December 2008 were identified in Hospital Episode Statistics, the database of admissions to English National Health Service hospitals. Children were included if they had diagnostic codes for a cleft as well as procedure codes for a primary surgical cleft repair. Children with codes indicating additional congenital anomalies or syndromes were excluded as their additional problems could have determined when and where they were treated. RESULTS: We identified 10,892 children with a cleft. 21.0% were excluded because of additional anomalies or syndromes. Of the remaining 8,606 patients, 30.4% had a surgical lip repair only, 41.7% a palate repair only, and 28.0% both a lip and palate repair. The number of hospitals that carried out these primary repairs reduced from 49 in 1997 to 13, with 11 of these performing repairs on at least 40 children born in 2008. The number of surgeons responsible for repairs reduced from 98 to 26, with 22 performing repairs on at least 20 children born in 2008. In the same period, average length of hospital stay reduced from 3.8 to 3.0 days for primary lip repairs, from 3.8 to 3.3 days for primary palate repairs, and from 4.6 to 2.6 days for combined repairs with no evidence for a change in emergency readmission rates. The speed of centralisation varied with the earliest of the nine regions completing it in 2001 and the last in 2007. CONCLUSIONS: Between 1998 and 2007, cleft services in England were centralised. According to a survey among patients' parents, the quality of cleft care improved in the same period. Surgical care became more consistent with current recommendations. However, key outcomes, including facial appearance and speech, can only be assessed many years after the initial surgical treatment

Grommet Surgery in Children With Orofacial Clefts in England.

OBJECTIVE: To assess grommet insertion practice in the first 5 years of life among children with an orofacial cleft in England. DESIGN: Analysis of national administrative data of hospital admissions. SETTING: National Health Service hospitals, England. PATIENTS: Patients born between 1997 and 2005 who underwent surgical cleft repair. INTERVENTION: Children receiving grommets before the age of 5 years. OUTCOME MEASURES: The proportion of children receiving grommets before the age of 5 years, the timing of the first grommet insertion, and the proportion of children having repeat grommet insertions were examined according to cleft type, the absence or presence of additional anomalies, socioeconomic deprivation, and region of residence. RESULTS: The study included 8,269 children. Before the age of 5 years, 3,015 (36.5%) children received grommets. Of these, 33.2% received their first grommets at primary cleft repair and 33.3% underwent multiple grommet insertion procedures. The most common age for the first procedure was between 6 and 12 months. Children with a cleft affecting the palate were more likely to receive grommets than children with a cleft lip alone (45.5% versus 4.5%). Grommet insertion practice also varied according to year of birth, absence or presence of additional anomalies, socioeconomic deprivation, and region of residence. CONCLUSION: Grommets practice in children with a cleft appears to vary according to their clinical characteristics. The differences in practice observed according to deprivation and region of residence need to be further explored

Bichromatic dressing of a quantum dot detected by a remote second quantum dot

We demonstrate an information transfer mechanism between two dissimilar remote InAs/GaAs quantum dots weakly coupled to a common photonic crystal microcavity. Bichromatic excitation in the s state of one of the dots leads to the formation of dressed states due to the coherent coupling to the laser field, in resonance with the quantum dot. Information on the resulting dressed structure is read out through the photoluminescence spectrum of the other quantum dot, as well as the cavity mode. The effect is also observed upon exchange of the excitation and detection quantum dots. This quantum dot intertalk is interpreted in terms of a cavity-mediated coupling involving acoustic phonons. A master equation for a three-level system coherently pumped by the two lasers quantitatively describes the behavior of our system. Our result presents an important step towards scalable solid-state quantum networking based on coupled multi-quantum-dot-cavity systems, without the need to use identical quantum emittersThis work was supported by the Spanish MINECO under Contract No. MAT2011-22997, by CAM under Contract No. S2009/ESP-1503, and by the FP7 ITN Spin-optronics (237252). C.S-M. and E.C. acknowledge FPI gran